Since lemon fanfics are inappropriate, we should focus on their general characteristics from the official story. Asta is highly determined and energetic, always striving hard despite his lack of magic initially. Yuno, on the other hand, is more calm and has a natural talent for magic. They both have a strong bond as rivals and friends.
Mereoleona's fire - based powers and Goku's ki - based powers could create some really interesting interactions. For example, Mereoleona could use her fire to surround Goku, but Goku could use his ki to either dissipate the fire or even absorb some of its energy to power up his own attacks. Their powers might also clash in a way that creates new types of energy blasts that neither of them expected.
One possible plot could be that Mereoleona, being from her own universe with her unique set of powers, somehow gets transported to Goku's universe. Goku, being the friendly Saiyan he is, would be curious about her powers. They might start with a friendly sparring session where Goku is amazed by Mereoleona's ability to control and manipulate fire. Then, they could team up against a common enemy that threatens both of their universes, learning from each other's fighting styles along the way.
One great Mereoleona and Lemon fanfiction is 'The Unlikely Bond'. It explores how Lemon's unique skills interact with Mereoleona's powerful and fierce nature. It has a lot of action scenes and some really interesting character development.
Noelle could be a great addition. Her water magic is quite powerful and she has a complex relationship with both Asta and Yuno. She could be a source of both support and conflict in the fanfic. Another good character is Luck. His lightning magic and his rather unpredictable nature can add a lot of action and excitement to the story.
Asta would likely bring a new level of determination to the Crimson Lions. His never - give - up attitude could inspire the team members during tough battles.
Asta is still alive in the manga. The story keeps evolving with him at the center of the action. There have been many difficult situations, but he manages to overcome them without dying.